In the context of mitosis, anaphase is the stage where the chromosomes (which have already been duplicated and are in the form of sister chromatids) are separated to opposite poles of the cell.
From your observations:
- 19 cells have 2 groups of chromatids in the process of separating. This suggests that these cells are in anaphase where the chromatids are starting to separate.
Therefore, based on this information, the number of cells in anaphase is 19.